The present invention relates to an inspecting device for inspecting a thin film coating material applied to a material being treated. The device is, for example, employed for examining the quality of primer applied to peripheral portions of front glass, rear glass and the like of an automobile.
In assembling processes of the automobile, window glass such as front and rear glass is mounted to a window frame of an automobile body after its entier periphery is coated with a sealing material. Furthermore, prior to an application of the sealing material, black primer is applied to a surface of the window glass and the window frame so as to enhance the reliability of adhesion therebetween. Such an applying work of the sealing material and the primer utilizes a variety of types of manipulators, thus being automated.
These coating materials, however, usually vary a great deal in fluidity, surface condition and the like with temperature, or depending on whether or not they have contact with air, or the like. Also, the coated materials vary in applied condition with the used quantity, the applying speed, or the like. Consequently, it becomes relatively difficult to achieve the quantitative control of the materials in the coating process and to apply the materials in a constant state. Thus, the normal coating is not always expected. For example, there will often arise a problem that the applied primer has sheer portions because of its insufficient film thickness or that the coating per se becomes blurred owing to the insufficient amount of the primer used.
In the meantime, while the coating work is automated, as regards examining work an operator still directly of indirectly, for example through ITV (Industrial Television), see whether or not the coating is normally performed. Accordingly, as a result of the change of the operator's criterion, the quality of the coating is subject to irregularity and also examination errors are liable to occur. Besides, the labor spent on such examining work results in an increase in cost. Furthermore, since window glass that has undergone a black ceramic treatment on its peripheral portion is increasingly employed nowadays, it becomes almost impossible to examine with man's eyes the condition of the black primer being applied.
It is true that ITV may be utilized to effect an automatic examination, nevertheless difficulties are encountered in such examination because of the fact that the black ceramic treatment and the primer are identical in color. In addition to that there exists the problem that the high cost is involved since ITV is of comparatively large size and signal operations thereof are complicated.